Blood vessel embolism is referred to hereby as an obstruction of a blood vessel by blood clots, emboli, or other foreign substances. This is a major cause of mortality and morbidity in the United States, particularly when blood vessel embolism occurs in a pulmonary vein or a coronary artery. To prevent embolism from occurring, patients are commonly treated with anticoagulants or with thrombolytic agents. In some situations, reliance on drugs may be inappropriate where a patient has high risk of internal bleeding or sensitive to a particular drug.
A blood filtration device has been widely used to collect and remove the blood clots, emboli and foreign substance from a blood vessel. Nadal in U.S. Pat. No. 5,725,550 discloses a blood filtration unit that is to be implanted in a vessel of a patient's body, especially for the purposes of retaining blood clots. The implanted filtration unit, either permanently or temporarily, continues to collect blood clots or emboli. The collected junk, including blood emboli, blood clots, debris and any foreign substance, should be removed and disposed of out of the body. Alternately, the junk should be treated in situ so that the treated blood emboli or clots are so small that they do not pose any harm to the blood vessel or to the patient. A permanently implanted filter system may need frequent junk removal when the accumulation of clots or emboli is excessive.
Barnhart et al. in U.S. Pat. No. 5,893,869 discloses a percutaneous filter system for providing temporary filtering of emboli from the blood. The filter system comprises a deployable filtering element to trap the blood junk that includes blood emboli, blood clots, debris and any foreign substance. When the filtering element is so deployed within a blood vessel, the junks entrapped within the filtering element are funneled toward a venting lumen and are aspirated or otherwise removed therethrough.
The conventional filtering devices, such as the one disclosed in U.S. Pat. No. 5,893,869, employ a lumen passageway for removing the blood emboli or clots. There are several disadvantages related to the system having an aspiring lumen passageway. First, the size of a delivery catheter incorporating an aspiring passageway is bulkier than a catheter without such a luminal passageway. A bulky catheter cannot be used in a small blood vessel. This becomes a more critical issue, because blood clots are mostly often associated with a small blood vessel. Secondly, blood is simultaneously aspired along with the blood clots or emboli through a removing passageway. An external filtering unit may be required to filter the aspired blood and return the filtered blood back to the patient. A blood salvage unit is particularly useful for returning the autologous blood to the same patient because of fear of cross-contamination from donated blood. By salvaging the autologous blood, anticoagulant is added to the filtered blood to prevent undesired blood coagulation or blood clotting.
Therefore, there is a clinical need to treat the blood emboli or blood clots in situ. This is particularly beneficial for the implanted blood filtering system to reduce the accumulation of the blood clots inside the filtering element. The treated clots or emboli can generally be returned to the circulatory system without further post-treatment in situ.
RF therapeutic protocol has been proven to be highly effective when used by electrophysiologists for the treatment of tachycardia; by neurosurgeons for the treatment of Parkinson's disease; and by neurosurgeons and anesthetists for other RF procedures such as Gasserian ganglionectomy for trigeminal neuralgia and percutaneous cervical cordotomy for intractable pains. Radiofrequency energy can be applied to a biological material or debris through a bipolar electrode means, wherein the biological debris may comprise blood clots, blood emboli, foreign biological substance and the like. Other alternate energy or mechanical means may also be used in treating the entrapped biological debris.